Smoky black bean and sweet potato vegan burger recipe

Ingredients

• 450g sweet potatoes, (about 3 medium)
• 3 tbsp rapeseed or sunflower oil
• 1 onion, finely chopped
• ½ red pepper, diced
• 2 garlic cloves, crushed
• 1 tbsp smoky chipotle paste
• 1 tbsp ground flaxseed
• 1 x 380g carton black beans, rinsed and drained
• 125g cooked quinoa
• 2 tbsp chopped coriander
• zest and juice of ½ lime
• 2 tbsp polenta or cornmeal
• 150g vegan mayo, oat fraiche or dairy-free yogurt
• 1 tsp smoky chipotle paste
• ½ tbsp agave or maple syrup
• 4 burger buns, split - use gluten-free if needed
• Super slaw (see tip at the end of step 8)
• 1 ripe avocado, sliced
• a handful of cress or sprouted seeds (optional)